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Diffstat (limited to 'libjava/classpath/vm/reference/java/lang/VMProcess.java')
| -rw-r--r-- | libjava/classpath/vm/reference/java/lang/VMProcess.java | 402 |
1 files changed, 402 insertions, 0 deletions
diff --git a/libjava/classpath/vm/reference/java/lang/VMProcess.java b/libjava/classpath/vm/reference/java/lang/VMProcess.java new file mode 100644 index 000000000..c41d7cc0c --- /dev/null +++ b/libjava/classpath/vm/reference/java/lang/VMProcess.java @@ -0,0 +1,402 @@ +/* java.lang.VMProcess -- VM implementation of java.lang.Process + Copyright (C) 2004, 2005 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package java.lang; + +import java.io.File; +import java.io.IOException; +import java.io.InputStream; +import java.io.OutputStream; +import java.util.HashMap; +import java.util.Iterator; +import java.util.LinkedList; +import java.util.List; +import java.util.Map; + +/** + * Represents one external process. Each instance of this class is in + * one of three states: INITIAL, RUNNING, or TERMINATED. The instance + * is {@link Object#notifyAll notifyAll()}'d each time the state changes. + * The state of all instances is managed by a single dedicated thread + * which does the actual fork()/exec() and wait() system calls. User + * threads {@link Object#wait()} on the instance when creating the + * process or waiting for it to terminate. + * + * <p> + * See + * <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11801">GCC bug + * #11801</a> for the motivation behind the design of this class. + * + * @author Archie Cobbs + * @see Process + * @see Runtime#exec(String) + */ +final class VMProcess extends Process +{ + + // Possible states for a VMProcess + private static final int INITIAL = 0; + private static final int RUNNING = 1; + private static final int TERMINATED = 2; + + // Dedicated thread that does all the fork()'ing and wait()'ing. + static Thread processThread; + + // New processes waiting to be spawned by processThread. + static final LinkedList workList = new LinkedList(); + + // Return values set by nativeReap() when a child is reaped. + // These are only accessed by processThread so no locking required. + static long reapedPid; + static int reapedExitValue; + + // Information about this process + int state; // current state of process + final String[] cmd; // copied from Runtime.exec() + final String[] env; // copied from Runtime.exec() + final File dir; // copied from Runtime.exec() + Throwable exception; // if process failed to start + long pid; // process id + OutputStream stdin; // process input stream + InputStream stdout; // process output stream + InputStream stderr; // process error stream + int exitValue; // process exit value + boolean redirect; // redirect stderr -> stdout + + // + // Dedicated thread that does all the fork()'ing and wait()'ing + // for external processes. This is needed because some systems like + // Linux use a process-per-thread model, which means the same thread + // that did the fork()/exec() must also do the wait(). + // + private static class ProcessThread extends Thread + { + + // Max time (in ms) we'll delay before trying to reap another child. + private static final int MAX_REAP_DELAY = 1000; + + // Processes created but not yet terminated; maps Long(pid) -> VMProcess + // Only used in run() and spawn() method from this Thread, so no locking. + private final HashMap activeMap = new HashMap(); + + // We have an explicit constructor, because the default + // constructor will be private, which means the compiler will have + // to generate a second package-private constructor, which is + // bogus. + ProcessThread () + { + } + + public void run() + { + final LinkedList workList = VMProcess.workList; + while (true) + { + + // Get the next process to spawn (if any) and spawn it. Spawn + // at most one at a time before checking for reapable children. + VMProcess process = null; + synchronized (workList) + { + if (!workList.isEmpty()) + process = (VMProcess)workList.removeFirst(); + } + + if (process != null) + spawn(process); + + + // Check for termination of active child processes + while (!activeMap.isEmpty() && VMProcess.nativeReap()) + { + long pid = VMProcess.reapedPid; + int exitValue = VMProcess.reapedExitValue; + process = (VMProcess)activeMap.remove(new Long(pid)); + if (process != null) + { + synchronized (process) + { + process.exitValue = exitValue; + process.state = TERMINATED; + process.notify(); + } + } + else + System.err.println("VMProcess WARNING reaped unknown process: " + + pid); + } + + + // If there are more new processes to create, go do that now. + // If there is nothing left to do, exit this thread. Otherwise, + // sleep a little while, and then check again for reapable children. + // We will get woken up immediately if there are new processes to + // spawn, but not if there are new children to reap. So we only + // sleep a short time, in effect polling while processes are active. + synchronized (workList) + { + if (!workList.isEmpty()) + continue; + if (activeMap.isEmpty()) + { + processThread = null; + break; + } + + try + { + workList.wait(MAX_REAP_DELAY); + } + catch (InterruptedException e) + { + /* ignore */ + } + } + } + } + + // Spawn a process + private void spawn(VMProcess process) + { + + // Spawn the process and put it in our active map indexed by pid. + // If the spawn operation fails, store the exception with the process. + // In either case, wake up thread that created the process. + synchronized (process) + { + try + { + process.nativeSpawn(process.cmd, process.env, process.dir, + process.redirect); + process.state = RUNNING; + activeMap.put(new Long(process.pid), process); + } + catch (ThreadDeath death) + { + throw death; + } + catch (Throwable t) + { + process.state = TERMINATED; + process.exception = t; + } + process.notify(); + } + } + } + + // Constructor + private VMProcess(String[] cmd, String[] env, File dir, boolean redirect) + throws IOException + { + + // Initialize this process + this.state = INITIAL; + this.cmd = cmd; + this.env = env; + this.dir = dir; + this.redirect = redirect; + + // Add process to the new process work list and wakeup processThread + synchronized (workList) + { + workList.add(this); + if (processThread == null) + { + processThread = new ProcessThread(); + processThread.setDaemon(true); + processThread.start(); + } + else + { + workList.notify(); + } + } + + // Wait for processThread to spawn this process and update its state + synchronized (this) + { + while (state == INITIAL) + { + try + { + wait(); + } + catch (InterruptedException e) + { + /* ignore */ + } + } + } + + // If spawning failed, rethrow the exception in this thread + if (exception != null) + { + exception.fillInStackTrace(); + if (exception instanceof IOException) + throw (IOException)exception; + + if (exception instanceof Error) + throw (Error)exception; + + if (exception instanceof RuntimeException) + throw (RuntimeException)exception; + + throw new RuntimeException(exception); + } + } + + // Invoked by native code (from nativeSpawn()) to record process info. + private void setProcessInfo(OutputStream stdin, + InputStream stdout, InputStream stderr, long pid) + { + this.stdin = stdin; + this.stdout = stdout; + if (stderr == null) + this.stderr = new InputStream() + { + public int read() throws IOException + { + return -1; + } + }; + else + this.stderr = stderr; + this.pid = pid; + } + + /** + * Entry point from Runtime.exec(). + */ + static Process exec(String[] cmd, String[] env, File dir) throws IOException + { + return new VMProcess(cmd, env, dir, false); + } + + static Process exec(List cmd, Map env, + File dir, boolean redirect) throws IOException + { + String[] acmd = (String[]) cmd.toArray(new String[cmd.size()]); + String[] aenv = new String[env.size()]; + + int i = 0; + Iterator iter = env.entrySet().iterator(); + while (iter.hasNext()) + { + Map.Entry entry = (Map.Entry) iter.next(); + aenv[i++] = entry.getKey() + "=" + entry.getValue(); + } + + return new VMProcess(acmd, aenv, dir, redirect); + } + + public OutputStream getOutputStream() + { + return stdin; + } + + public InputStream getInputStream() + { + return stdout; + } + + public InputStream getErrorStream() + { + return stderr; + } + + public synchronized int waitFor() throws InterruptedException + { + while (state != TERMINATED) + wait(); + return exitValue; + } + + public synchronized int exitValue() + { + if (state != TERMINATED) + throw new IllegalThreadStateException(); + return exitValue; + } + + public synchronized void destroy() + { + if (state == TERMINATED) + return; + + nativeKill(pid); + + while (state != TERMINATED) + { + try + { + wait(); + } + catch (InterruptedException e) + { + /* ignore */ + } + } + } + + /** + * Does the fork()/exec() thing to create the O/S process. + * Must invoke setProcessInfo() before returning successfully. + * This method is only invoked by processThread. + * + * @throws IOException if the O/S process could not be created. + */ + native void nativeSpawn(String[] cmd, String[] env, File dir, + boolean redirect) + throws IOException; + + /** + * Test for a reapable child process, and reap if so. Does not block. + * If a child was reaped, this method must set reapedPid and + * reapedExitValue appropriately before returning. + * This method is only invoked by processThread. + * + * @return true if a child was reaped, otherwise false + */ + // This is not private as it is called from an inner class. + static native boolean nativeReap(); + + /** + * Kill a process. This sends it a fatal signal but does not reap it. + */ + private static native void nativeKill(long pid); +} |